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relation between the value of direct current potential Vp as applied at points I and 2 to the D. C. path. and the pontial Vs obtained. in the secondary winding of the transformer T2 of Fig. 1. Asis readily apparent when point I is negative with respect to point 2, no A. C. will be passed except for those potentials less than Q5 v. When points I and 2 are at equal potentials tin value of Vs is approximately 8 v. When point I is 2 v. positive with respect to point 2, the potential Vs obtained is 42 v.

Fig. 3 shows a combination of two static switches, each of which has the same characilsistics as that illustrated by Fig. 2; They have a common feeding transformer Tr, of which the two secondary windings 3 4 and l--i respete tively are each equivalent to the secondary winding of transformer Tl in Fig. 1. The secondary windings II-I2 and II-I4 of output transformers Ta and Tg are connected in seria in such a manner that the alternating potentials indud in these two windings are aiding.

Forthepurposeofusing this arrangementfos detecting the presence of one particular potential. e. g. a potential forvX volts. the electric midpoints of windings 8-4 and 5-4 are connected together and to the source of electric potential VP which has to be detected. The electric midpointofwinding'I-lisconnectedtoapotentiai which is o. g., 2 v. noitivevwith rpect to ami the electric midpoint of winding B--III is con nested to an electric potential which is e. g. 2 v. positive with respect to the potential X. The effect of this arrangement is illustrated in rig.. 5.

In this figure, curve a reprents the response curve of the static switch shown at the top of Fig. 3, the curve indicated by b shows the response curve of the static switch indicated at the bottom of Fig. 3 whereas the curve e shows thesumofthepotentialsrepresentedbycurvesa and b and which will therefore he present betweenterminals II andilinFliLB.

Itwillbeseenthatifthepotsntialvpwere at apolnt 2 v. negative with respect to potential X, there would be equal potentials at the eleotric midpoints of windings 3.-# and 1 4 ReferencetoFigZwillshowthatinthiscaeethe potential created in theseoondary winding I I--H- of Ts is aproxlmately 8v. At the saine time the diil'erence of potential betwn the electric midpoints of windings i--Q and l--II would bed v. and this potentlal would be connccizedinsucha manner that the rectiilcrs insertedbetweenthese two windings would be rendered conductive. Reference to Fig. 2 shows that. when the-static switch is subjected to a potential of i v. in the conductive direction of the rectifier-s, the poten tial Vs is approximately 50 v., and accordingly the curve b in Fig. 5 shows this value at the point of potential X-2 v. The sum of the potentials in windings ii-II and Il-ie atx-2 v. willaccordinglybe58v.asindicatsdbycurvec. From the figure it is clear that if the potential Vs indicated by curve c were applied toa. Y i. discharge tube which required apotmtial Vb o e. g. 'IU v. to cause its ionisation, asumcientpotcntial Vs would be present only when Vp reaches the value X1: approximately l v.

An alternative arrangement to ohtainthe same eeot i's shown by Fig. 4, which shows the use of a single transformer Ts. instead of the' two transformers T2 and Ts oi' Fig. 3. The potential Vb is now connected to the electric midpoint of the winding 1 8 of this transfonner. and the potentials X-2 v. and X+-2 v.. which determine the potential X at which the signal receiver should operate, are connected to the midpoints od winding #-4 and l-B oi transformer T1, respectively. This figure is completed to snow the manner in which the secondary winding of transformer Ta may be connected to the control electrode of a gaseous discharge tube CC, in series with the discharge space of which a signal responding device R is connected.

It will be noticed that when no potential at all is connected to the point marked Vp in Figs. 3 and 4 a direct current will flow from the potential X+2 v. to the potential X-2 v., through both direct current paths of the static switches, In series whereby an alternating current would be transmitted to the transformer Tn, of sumcient potential to cause the functioning of the gaseous discharge tube. In order to obviate this, the point Vp is permanently connected to e. g. a ground potential through a resistance of high value W. This potential is of such value that it is either negative with respect to X2, or positive with respect to X+2, and thereby prevents direct current owing through one of the two direct current paths mentioned so that only this static switch alternating current potential, and the potential Vb required to produce functioning of the discharge tube cannot be reached. When a potential Vp is connected which should cause the functioning of the gane ous discharge tube, the resistance through which this potential is provided should be low enough to render the effect of the connection of ground through resistance W negligible.

It may be observed from the curves shownl in Fig. 5 that the arrangement as shown in Figs. 8 and 4 is capable of functioning correctly onlyv when the maximum potential Vs produced by each individual static switch is substantially lem than the minimum potential required to ionise the gaseous discharge tube, whereas at the same time the sum of the potentials produced by each static switch at the operating potential X should exceed the maximum potential Vb required to ionise the discharge tube.

It will be clear, that from Fig. 5 the operating limits obtainable with this arrangement will not be very large, since the potential Vs produced by a single static switch is already relatively near to the ionisation potential Vb. These limits can be somewhat increased by taking instead of the reference potentials X+2 and X4. other potentials which are farther apart but in each case the false" potential, produced by one staticswitch will be more than half the ionisa.- tion potential Vb.

Taking the reference potentials farther apart has in itself the consequence that the range of potentials at which the discharge tube will function is increased, so that it is not possible, with this arrt, to restrict the operation of the system to a sharply defined potential X.

Better results are obtained with the arrangements indicated by Figs. 9 and l0. Considering Fig. 9 first, this di'ers from Fig. 3 in that the ocnnections to winding s-Is of transformer Ta have been reversed. As a consequence, the potentials induced in windings II-IZ and I3-Il of transformers T: and Ta, which are connected in series, now counteract each other, so that the total potential Vs will be aero, when the potentials produced by transformers T2 and Ts are equal. Besides the electric midpoints of wind!- 

